bjoernager/rust
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try to avoid some layout_of calls

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This commit is contained in:
Ralf Jung 2023-09-21 07:26:11 +02:00
parent 23fd2860fa
commit 0eff07b748
8 changed files with 75 additions and 71 deletions
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67
compiler/rustc_const_eval/src/interpret/cast.rs
View file

@ -24,40 +24,43 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
cast_ty: Ty<'tcx>,
dest: &PlaceTy<'tcx, M::Provenance>,
) -> InterpResult<'tcx> {
// `cast_ty` will often be the same as `dest.ty`, but not always, since subtyping is still
// possible.
let cast_layout =
if cast_ty == dest.layout.ty { dest.layout } else { self.layout_of(cast_ty)? };
// FIXME: In which cases should we trigger UB when the source is uninit?
match cast_kind {
CastKind::PointerCoercion(PointerCoercion::Unsize) => {
let cast_ty = self.layout_of(cast_ty)?;
self.unsize_into(src, cast_ty, dest)?;
self.unsize_into(src, cast_layout, dest)?;
}
CastKind::PointerExposeAddress => {
let src = self.read_immediate(src)?;
let res = self.pointer_expose_address_cast(&src, cast_ty)?;
let res = self.pointer_expose_address_cast(&src, cast_layout)?;
self.write_immediate(*res, dest)?;
}
CastKind::PointerFromExposedAddress => {
let src = self.read_immediate(src)?;
let res = self.pointer_from_exposed_address_cast(&src, cast_ty)?;
let res = self.pointer_from_exposed_address_cast(&src, cast_layout)?;
self.write_immediate(*res, dest)?;
}
CastKind::IntToInt | CastKind::IntToFloat => {
let src = self.read_immediate(src)?;
let res = self.int_to_int_or_float(&src, cast_ty)?;
let res = self.int_to_int_or_float(&src, cast_layout)?;
self.write_immediate(*res, dest)?;
}
CastKind::FloatToFloat | CastKind::FloatToInt => {
let src = self.read_immediate(src)?;
let res = self.float_to_float_or_int(&src, cast_ty)?;
let res = self.float_to_float_or_int(&src, cast_layout)?;
self.write_immediate(*res, dest)?;
}
CastKind::FnPtrToPtr | CastKind::PtrToPtr => {
let src = self.read_immediate(src)?;
let res = self.ptr_to_ptr(&src, cast_ty)?;
let res = self.ptr_to_ptr(&src, cast_layout)?;
self.write_immediate(*res, dest)?;
}
@ -140,6 +143,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
CastKind::Transmute => {
assert!(src.layout.is_sized());
assert!(dest.layout.is_sized());
assert_eq!(cast_ty, dest.layout.ty); // we otherwise ignore `cast_ty` enirely...
if src.layout.size != dest.layout.size {
let src_bytes = src.layout.size.bytes();
let dest_bytes = dest.layout.size.bytes();
@ -164,15 +168,14 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
pub fn int_to_int_or_float(
&self,
src: &ImmTy<'tcx, M::Provenance>,
cast_ty: Ty<'tcx>,
cast_to: TyAndLayout<'tcx>,
) -> InterpResult<'tcx, ImmTy<'tcx, M::Provenance>> {
assert!(src.layout.ty.is_integral() || src.layout.ty.is_char() || src.layout.ty.is_bool());
assert!(cast_ty.is_floating_point() || cast_ty.is_integral() || cast_ty.is_char());
assert!(cast_to.ty.is_floating_point() || cast_to.ty.is_integral() || cast_to.ty.is_char());
let layout = self.layout_of(cast_ty)?;
Ok(ImmTy::from_scalar(
self.cast_from_int_like(src.to_scalar(), src.layout, cast_ty)?,
layout,
self.cast_from_int_like(src.to_scalar(), src.layout, cast_to.ty)?,
cast_to,
))
}
@ -180,48 +183,46 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
pub fn float_to_float_or_int(
&self,
src: &ImmTy<'tcx, M::Provenance>,
cast_ty: Ty<'tcx>,
cast_to: TyAndLayout<'tcx>,
) -> InterpResult<'tcx, ImmTy<'tcx, M::Provenance>> {
use rustc_type_ir::sty::TyKind::*;
let layout = self.layout_of(cast_ty)?;
let val = match src.layout.ty.kind() {
// Floating point
Float(FloatTy::F32) => self.cast_from_float(src.to_scalar().to_f32()?, cast_ty),
Float(FloatTy::F64) => self.cast_from_float(src.to_scalar().to_f64()?, cast_ty),
Float(FloatTy::F32) => self.cast_from_float(src.to_scalar().to_f32()?, cast_to.ty),
Float(FloatTy::F64) => self.cast_from_float(src.to_scalar().to_f64()?, cast_to.ty),
_ => {
bug!("Can't cast 'Float' type into {}", cast_ty);
bug!("Can't cast 'Float' type into {}", cast_to.ty);
}
};
Ok(ImmTy::from_scalar(val, layout))
Ok(ImmTy::from_scalar(val, cast_to))
}
/// Handles 'FnPtrToPtr' and 'PtrToPtr' casts.
pub fn ptr_to_ptr(
&self,
src: &ImmTy<'tcx, M::Provenance>,
cast_ty: Ty<'tcx>,
cast_to: TyAndLayout<'tcx>,
) -> InterpResult<'tcx, ImmTy<'tcx, M::Provenance>> {
assert!(src.layout.ty.is_any_ptr());
assert!(cast_ty.is_unsafe_ptr());
assert!(cast_to.ty.is_unsafe_ptr());
// Handle casting any ptr to raw ptr (might be a fat ptr).
let dest_layout = self.layout_of(cast_ty)?;
if dest_layout.size == src.layout.size {
if cast_to.size == src.layout.size {
// Thin or fat pointer that just hast the ptr kind of target type changed.
return Ok(ImmTy::from_immediate(**src, dest_layout));
return Ok(ImmTy::from_immediate(**src, cast_to));
} else {
// Casting the metadata away from a fat ptr.
assert_eq!(src.layout.size, 2 * self.pointer_size());
assert_eq!(dest_layout.size, self.pointer_size());
assert_eq!(cast_to.size, self.pointer_size());
assert!(src.layout.ty.is_unsafe_ptr());
return match **src {
Immediate::ScalarPair(data, _) => Ok(ImmTy::from_scalar(data, dest_layout)),
Immediate::ScalarPair(data, _) => Ok(ImmTy::from_scalar(data, cast_to)),
Immediate::Scalar(..) => span_bug!(
self.cur_span(),
"{:?} input to a fat-to-thin cast ({} -> {})",
*src,
src.layout.ty,
cast_ty
cast_to.ty
),
Immediate::Uninit => throw_ub!(InvalidUninitBytes(None)),
};
@ -231,10 +232,10 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
pub fn pointer_expose_address_cast(
&mut self,
src: &ImmTy<'tcx, M::Provenance>,
cast_ty: Ty<'tcx>,
cast_to: TyAndLayout<'tcx>,
) -> InterpResult<'tcx, ImmTy<'tcx, M::Provenance>> {
assert_matches!(src.layout.ty.kind(), ty::RawPtr(_) | ty::FnPtr(_));
assert!(cast_ty.is_integral());
assert!(cast_to.ty.is_integral());
let scalar = src.to_scalar();
let ptr = scalar.to_pointer(self)?;
@ -242,17 +243,16 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
Ok(ptr) => M::expose_ptr(self, ptr)?,
Err(_) => {} // Do nothing, exposing an invalid pointer (`None` provenance) is a NOP.
};
let layout = self.layout_of(cast_ty)?;
Ok(ImmTy::from_scalar(self.cast_from_int_like(scalar, src.layout, cast_ty)?, layout))
Ok(ImmTy::from_scalar(self.cast_from_int_like(scalar, src.layout, cast_to.ty)?, cast_to))
}
pub fn pointer_from_exposed_address_cast(
&self,
src: &ImmTy<'tcx, M::Provenance>,
cast_ty: Ty<'tcx>,
cast_to: TyAndLayout<'tcx>,
) -> InterpResult<'tcx, ImmTy<'tcx, M::Provenance>> {
assert!(src.layout.ty.is_integral());
assert_matches!(cast_ty.kind(), ty::RawPtr(_));
assert_matches!(cast_to.ty.kind(), ty::RawPtr(_));
// First cast to usize.
let scalar = src.to_scalar();
@ -261,8 +261,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
// Then turn address into pointer.
let ptr = M::ptr_from_addr_cast(&self, addr)?;
let layout = self.layout_of(cast_ty)?;
Ok(ImmTy::from_scalar(Scalar::from_maybe_pointer(ptr, self), layout))
Ok(ImmTy::from_scalar(Scalar::from_maybe_pointer(ptr, self), cast_to))
}
/// Low-level cast helper function. This works directly on scalars and can take 'int-like' input

2
compiler/rustc_const_eval/src/interpret/discriminant.rs
View file

@ -163,7 +163,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
// Cast bits from tag layout to discriminant layout.
// After the checks we did above, this cannot fail, as
// discriminants are int-like.
let discr_val = self.int_to_int_or_float(&tag_val, discr_layout.ty).unwrap();
let discr_val = self.int_to_int_or_float(&tag_val, discr_layout).unwrap();
let discr_bits = discr_val.to_scalar().assert_bits(discr_layout.size);
// Convert discriminant to variant index, and catch invalid discriminants.
let index = match *ty.kind() {